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technical director

For more information, please contact Oscar Franzese, Technical Director, at or (865) 946-1304.

performance based Brake tester (PBBt)

PBBTThe ORNL’s Center for Transportation Analysis, in collaboration with the FMCSA and the Tennessee Highway Patrol (THP) Commercial Vehicle Enforcement (CVE), conducted a Performance-Based Brake Tester (PBBT) Valuation Study. The purpose of the study was to determine the PBBT’s ability to increase the number of contacts with commercial motor vehicles (CMVs) and explore how the PBBT affects the CMV out-of-service (OOS) rate. The PBBT is a roller dynamometer which measures the vehicle’s established brake force and calculates brake efficiency to indicate the effectiveness of the vehicle’s brakes. Several test scenarios were employed using North American Standard (NAS) Level-1, 2, and 3 CMV inspection criteria. The first three scenarios employed both an NAS inspection (Level-1, 2, or 3) and PBBT test for a given test vehicle. In the fourth testing scenario the PBBT was used as a screening tool to determine if Level-1 inspections were necessary. A fifth scenario, designed to determine the time savings associated with the use of an inspection pit, involved conducting a series of Level-1 inspections at the Greene and Knox County CMV Inspection Stations. Two additional scenarios were included as a result of initial analysis: the use of a Level-2 in conjunction with a PBBT and the use of the PBBT in a stand-alone inspection (NAS Level-4). Inspections conducted using an inspection pit saved only 2.4 minutes over having to crawl underneath the CMV via an inspection creeper, but resulted in a greater OOS rate. The results of this study indicate that it takes an average of 16 minute to conduct a Level-4 PBBT test and approximately 9 minutes to conduct a PBBT in conjunction with an NAS-Level inspection. On average, it takes 3.1 minutes longer to conduct a PBBT test than the brake stroke measurement currently conducted as part of the NAS Level-1 inspection. Based on this testing (including only the time to conduct the inspection) NAS Level-2 and 3 inspections each take an average of 10.3 minutes and 6.6 minutes, respectively. For this short-term test, the NAS Level-1 scenario resulted in the highest OOS rate compared to the other scenarios.

Based on the testing times, the use of the Level-3 inspection would result in the highest number of CMV contacts in a given period of time. In most cases, the NAS Level-4 special inspection using the PBBT screening test was found to be the least time-consuming, but this inspection does not involve a check of the driver’s credentials or equipment. The data collected in this study was used to develop a worksheet to help determine the most effective use of personnel in a given time period based on typical inspection times and OOS rates.

See Poster ( PDF, 12MB) and Draft Report (PDF, 1MB)